Analysis and Interpretation of Polygraphic Sleep Recordings and Overnight Sleep and Fatigue Indices During a Three-Night Simulation of Noise Conditions Aboard the International Space Station

Fifteen healthy volunteers, were grouped in teams of five. Two teams were exposed to noise during the day only (day noise group; 5 males and 5 females), 2 teams were exposed day and night (all noise groups; 5 males and 5 females), and 1 team was not exposed to any noise (control group of 2 males and 3 females). Participants were equipped for continuous ambulatory recording of EEG, EOG and EMG and completed 9 x 1-hour experimental blocks during the experiment. The overnight sleep periods were scheduled between 22h00 and 06h00. Electroencephalogram (EEG) data was recorded continuously from Day 1 to Day 4. All groups spent more time in lighter sleep stages and had very little SWS (less than 8%). Since sleep composition was affected in all three groups we can hypothesized that they were affected by the cloistered environment. The most probable cause of this SWS reduction is exposure to a cloistered environment. Noise exposure, did not show an impact on SWS since no significant difference were found between the groups. In contrast, an effect of the degree of exposure to noise was found on the percentage of REM sleep. The all noise group showed less percentage of REM sleep than the day noise group, which in turn showed less percentage of REM sleep than the control group. Objective measurement of sleepiness through the 4 min eyes closed task showed that subjects exposed to noise continuously tended to have more difficulty resisting sleep than control or day noise groups. Even though